Preparation method of 5-trifluoromethyl uracil

The invention provides a preparation method of 5-trifluoromethyl uracil, and relates to the technical field of synthesis of medical intermediates. According to the invention, triethyl orthoformate, urea and dimethyl malonate are used as raw materials, condensation, saponification, cyclization and fluorination are carried out to obtain the target product 5-trifluoromethyl uracil, and the atom economy is high. Ethanol is removed in time in the condensation reaction process, the amount of the impurity 2-aminomethylene-dimethyl propionate is greatly reduced, and the yield of the target product is increased. The temperature of the saponification reaction is controlled within 40 DEG C, so that decarboxylation impurities (uracil) are prevented from being generated at the reflux temperature, and the yield of the target product is increased. The preparation method provided by the invention has the advantages of high product yield, high purity, easily available raw materials, low cost and simple process, and is suitabl